"We'll see how it goes but maybe I'll do one more season," the American, back in action at 37 and currently taking part in the Tour Down Under in Australia, told French sports daily L'Equipe.

"I'm having fun at the moment and I dont want to fix myself a limit," he added.

Armstrong announced last year he was making a comeback to promote cancer awareness and has not ruled out the possibility of an eighth Tour de France win.

"I have already won on the road but I have never won the heart of the French people and that's probably the most difficult", said Armstrong, whose seven Tour de France victories have long been the subject of unfounded accusations over doping.

Asked why he had turned down an offer by the French Anti-Doping Agency (AFLD) to retest his urine samples from the 1999 Tour, Armstrong said: "Because I have never cheated, neither in 1999 nor in 2000, 2005 or 2009."

Armstrong said he had been tested 13 times since announcing his comeback and added he was in great shape.

"My age, of course," he said when asked for the difference between now and when he announced his retirement in 2005. "But I'm in the best shape I've ever been in. You can't compare January 2009 with 2001 or 2002, for instance. I'm in much better shape.

"No, don't put that in," he told L'Equipe. "The French don't like to hear that. Say I'm in awful shape."